The synthetic bugs these researchers created would simply reduce the two step process of cornstarch -> lactate -> PLA into one: cornstarch -> PLA. The US already subsidizes enormous amounts of maize farming, might as well use it for plastics that will biodegrade.

Not to mention that the carbon in the corn sugar would have been metabolized and exhaled as carbon dioxide anyways. The fear mongering about this being bad for climate change is clearly over the top.

I'm with Adam on this. If we stop using oil and gas for fuel (and I think we will, mostly, eventually), there will be cheap and plentiful oil and gas to make ethylene and all of its cousins for plastic and rubber. PLA's biodegradability only matters if you plan to dispose of it in the ocean or by throwing it in the forest. In a dry, sunless landfill, PLA won't degrade any more than newspaper (landfill archeologists find undegraded newspapers decades old in mint condition). Plastic bags in the ocean are a trash problem, not a plastic problem. So on the one hand you have oil based polymers, with cheap raw materials, no real effect on CO2 in the atmosphere, and 60 years of installed base and technology to make them. On the other you have an expensive bioprocess, fed by products from fields that could otherwise grow food, which will take up just as much room and degrade just as little in a landfill, and, as a bonus, will lose strength and blemish as it grows old when used in a long term application. I don't see how you can make an economic or environmental case for PLA.

Two things. First, it's important to realize that green implies more than just atmospheric pollution. I believe most people associate green with more than just climate change. While there are probably a few focused solely on climate change I don't think this represents everyone. After all, recycling is regarded as green and doesn't have a major impact on atmospheric carbon.

Second, it doesn't sound like the feed stock used is oil so this will probably be entirely carbon neutral. It uses the existing carbon cycle rather than bringing carbon back in that has been safely buried for millions of years. It will biodegrade and go back into the system and is probably generated from organic feedstock. Very little (if any) net change in atmospheric carbon.

This is an incredible article, and an important discovery by Cargill. Producing packaging that biodegrades over a matter of years (instead of hundreds or thousands of years) would clean up the world's landfills, parks, and water resources. Nice job Economist.

Adam1, if you want to think about the dangers of plastic bags, read about the Pacific Trash Vortex, particularly the part about how when plastic bags degrade into little pieces, they pick up PCBs, so that when they're eaten by little fish they get biomagnified into the larger fish we eat. Tuna, anyone? This is only one example of the damages of plastic for humans. Biodegradable plastic is an important discovery for the health and welfare of large numbers of PEOPLE. The only question is, will individuals in society be smart enough to continue to push for it?

Oil turned into plastic, has hardly any impact on climate. The carbon is locked into the plastic material. That is, as long as the plastic won't disintegrate. Fast degrading release the CO2, the product of disintegration, into the atmosphere.

And here is a dilemma - do we prefer fast-degrading plastic, which is to leave our parks clean, and our atmosphere with higher CO2 levels, or should we prefer the other non-degradable plastics.

Some 10% of oil is turned into plastics. The faster it is degraded, the faster CO2 is emitted back to the atmosphere, with the possible climatic effects.

Calling this development "green" is somewhat misleading. There is hardly any effect on the climate, and that is mostly what people expect when some oil-related item is named "green".

Since the most common feedstock for the plastics is natural gas, with abundant supplies , for 100 years or more, such an effort of finding substitute for plastic-making serves no need. No climate effects, no depletion in the next 100 years of gas resources, low prices - what is this good for?
Take the scientific resources employed here, and devote it to real energy R&D.